The present invention relates to passive thin film devices that compensate for signal losses over trace conductors at printed circuit assemblies and/or connectors and/or transmission lines and passively augment the impedance characteristic of the relevant conductive pathway, among other applications.
Dielectric and conductor losses, cross talk, reflections and noise, among a variety of other parasitic and signal degrading conditions, can impair operation of high frequency digital circuits, such as used in many telecommunication and networking applications. These problems are especially apparent at frequencies and data transfer rates in excess of 1.0 GHz, where reduced performance means reduced bandwidth and more hardware to achieve any desired result.
Cross talk can develop between signal lines and reflections and noise can develop from terminations. The resultant losses or signal attenuation, noise and cross talk can distort and reduce the fidelity of transmitted data signals. Delays can also occur with a resultant loss of synchronization in data conveyed between data supply conductors and responding circuitry. The degradation of signal fidelity and loss of synchronization make it difficult to distinguish the information content of transmitted data. High frequency circuit designers therefore expend considerable effort to minimize sources of noise, cross talk and signal attenuation.
Optical fiber, active repeater/amplifier devices and/or special materials can be used to improve signal integrity. Such devices, however, frequently require increased power and increased physical space for the circuitry. These improvements can also be relatively costly to implement.
Passive devices, such as capacitors or simple RC circuits, have been mounted to the top and bottom surfaces of printed circuit boards in close association to populated circuitry to enhance signal quality. Such mountings can be costly to implement and cannot be readily re-worked, if changes or fine-tuning is required. Embedded capacitors have also been incorporated into integrated circuit packages as shown at U.S. Pat. No. 6,407,929.
The subject invention provides thin film devices or equalization modules constructed of planar copper component features (e.g. passive resistors, capacitors, inductors) and/or hybrid components that, for example, can be coupled to printed circuit assemblies (e.g. mother and daughter boards) to offset losses present in signal carrying conductors. The equalization modules can be coupled to individual trace conductors of a printed circuit assembly to provide a tailored impedance characteristic to passively compensate for inherent high frequency signal degradation. The modules can also be mounted in connectors that couple to a printed circuit assembly to compensate for anticipated high frequency losses over a designed bandwidth at selected trace conductors at the board. Improved signal fidelity and synchronization are thereby achieved over an expanded operational bandwidth
It is a primary object of the present invention to provide a passive thin film device that can be coupled to compensate for signal attenuation and degradation occurring in conductors conveying signals at gigahertz frequencies.
It is a further object of the invention to provide a device that includes thin film capacitor(s) and resistor(s) deposited on a ceramic substrate and wherein a thin film capacitor plate separately defines a device resistor.
It is a further object of the invention to provide a connector to a printed circuit assembly and/or cable containing several equalizer devices.
Various of the foregoing objects, advantages and distinctions of the invention are found in a passive, thin film module having one or more input and output terminations to a shunt resistor/capacitor pair constructed on a ceramic substrate and wherein a thin film capacitor plate separately defines a device resistor. A printed circuit connector is also disclosed that includes several modules tailored to compensate for signal loss/degradation at a coupled connector. Several of the foregoing equalizers of predetermined values are serially mounted to individual conductive paths or connector ports of a board/cable connector to compensate for anticipated trace conductor losses at a mating printed circuit assembly.
In another equalizer module construction, a multi-port, hybrid thin-film, RC filter circuit module configured on a ceramic substrate and used to improve impedance characteristic of transmission lines and/or trace conductors.
Still other objects, advantages and distinctions of the invention will become more apparent from the following description with respect to the appended drawings. Considered alternative constructions, improvements or modifications are described as appropriate. The description should not be literally construed in limitation of the invention. Rather, the scope of the invention should be broadly interpreted within the scope of the further appended claims.